1. Field of the Invention
The present invention relates to an ink-jet recording head having, in a single ink channel, a plurality of heating elements which can be independently driven. Furthermore, the present invention relates to an ink-jet recording method and apparatus using such ink-jet recording head.
2. Related Background Art
Most ink-jet recording apparatuses are known as printing apparatuses for printers, facsimile apparatuses, wordprocessors, copying machines, and the like. Of such apparatuses, an ink-jet recording apparatus that ejects ink by bubbles produced using heat energy as energy for ink ejection has recently become popular. As another application of an ink-jet recording apparatus of this type, an ink-jet printing apparatus for printing a predetermined pattern, design, synthesized image, or the like on cloth has become popular recently.
An ink-jet recording head used in the above-mentioned ink-jet recording apparatus uses electro-thermal conversion elements (to be also referred to as heaters hereinafter) as means for producing heat energy, and most ink-jet recording heads adopt an arrangement (to be also referred to as a single-heater arrangement hereinafter) that comprises a single heater in correspondence with a single ink channel. In contrast to this, some heads comprise a plurality of heaters in correspondence with a single ink channel (to be also referred to as a multi-heater arrangement hereinafter) for the following merits. Such head uses a plurality of heaters for the purpose of widening the range in which the ink ejection amount can be changed to attain gradation expression, and the ejection amount is changed by selecting the heaters to be driven or the number of heaters to be driven.
In one example of the arrangement, a plurality of heaters are arranged along the ink ejection direction in an ink channel communicating with an ejection orifice. By selecting the heaters to be driven or the number of heaters to be driven, the distances between the heaters to be driven and the ejection orifice are varied, thereby changing the ejection amount.
In another arrangement, a plurality of heaters having different surface areas are arranged in an ink channel, and the ink ejection amount is changed by selecting the heaters to be driven or the number of heaters to be driven as in the former arrangement. For example, such arrangement is disclosed in Japanese Patent Application Laid-Open No. 55-132259.
However, some problems remain unsolved to realize the above-mentioned multi-heater ink-jet recording head.
First, it is required to improve landing precision by improving the ink ejection velocity so as not only to vary the ink ejection amount but also to accomplish higher-quality recording. In order to achieve high-speed recording, the refill frequency of ink into the ink channel must also be improved.
Second, compatibility with single-heater ink-jet recording heads poses another problem. Most ink-jet recording heads are commercially available as expendables that are detachably mounted on ink-jet recording apparatuses in the form of cartridges that integrate tanks for storing ink, and are exchanged with new ones when ink in the tank is used up. On the other hand, an ink-jet recording apparatus which uses a single-heater ink-jet recording head has no arrangement for controlling driving of a multi-heater ink-jet recording head, but the multi-heater ink-jet recording head may be mounted on such ink-jet recording apparatus. For this reason, it is preferable to provide compatibility between the multi- and single-heater ink-jet recording heads so as to avoid confusion in the market.
It is an object of the present invention to provide an ink-jet recording method, ink-jet recording head, and ink-jet recording apparatus, which can improve the ejection characteristics represented by the ejection velocity and ejection amount when an ink-jet head having a plurality of electro-thermal conversion elements in correspondence with a single ink channel is used, and ink is ejected by driving the plurality of electro-thermal conversion elements.
It is another object of the present invention to provide an ink-jet recording method, ink-jet recording head, and ink-jet recording apparatus, which can realize high-speed recording by improving the refill frequency.
It is still another object of the present invention to provide an ink-jet recording head which is compatible with a head in which a single heater is arranged in correspondence with a single ink channel.
Other objects of the present invention will be understood from the following description of the embodiments.
An ink-jet recording method of the present invention uses an ink-jet recording head in which a plurality of electro-thermal conversion elements that can be independently driven are arranged in an ink channel communicating with an ejection orifice, and which bubbles ink by driving the electro-thermal conversion elements and ejects the ink from the ejection orifice, and relates to how to drive at least two of the electro-thermal conversion elements when the ink is bubbled by driving these electro-thermal conversion elements.
In one method, ink is ejected from the ejection orifice by relatively shifting the bubbling timings defined upon driving the at least two electro-thermal conversion elements within the range in which the ejection characteristics of ink do not deteriorate as compared to a case wherein the ink is bubbled by simultaneously driving the at least two electro-thermal conversion elements, e.g., within the range in which the ejection velocity of ink does not decrease, thus recording on a recording medium.
In another method, ink is ejected from the ejection orifice by relatively shifting the drive timings of the at least two electro-thermal conversion elements for bubbling ink within the range in which the ejection characteristics of ink do not deteriorate as compared to a case wherein the ink is bubbled by simultaneously driving the at least two electro-thermal conversion elements, e.g., within the range in which the ejection velocity of ink does not decrease, thus recording on a recording medium.
Alternatively, ink is ejected from the ejection orifice by relatively shifting the bubbling timings defined upon driving the at least two electro-thermal conversion elements within the range in which the ink ejection amount does not decrease as compared to a case wherein the ink is bubbled by simultaneously driving the at least two electro-thermal conversion elements, thus recording on a recording medium.
Or, ink is ejected from the ejection orifice by relatively shifting the drive timings of the at least two electro-thermal conversion elements for bubbling ink within the range in which the ink ejection amount does not decrease as compared to a case wherein the ink is bubbled by simultaneously driving the at least two electro-thermal conversion elements, thus recording on a recording medium.
Alternatively, if AT represents the relative shift period between the bubbling timings upon driving the individual electro-thermal conversion elements, ink is ejected from the ejection orifice by relatively shifting the bubbling timings within the following range to record on a recording medium:
0 less than |xcex94T| less than 0.5 xcexcs
An ink-jet recording head and ink-jet recording apparatus of the present invention have the above-mentioned means for shifting the bubbling timings of the electro-thermal conversion elements.
The present inventors found that macroscopically the ink ejection velocity tends to decrease as the shift period between the bubbling timings becomes larger when ink is ejected by driving two of a plurality of electro-thermal conversion elements arranged in an ink channel, and when the bubbling timings are shifted. When the ejection velocity and ejection amount were microscopically measured by decreasing the shift period between the bubbling timings, the present inventors found a new phenomenon in that the ink ejection velocity and ejection amount do not become maximum when ink is bubbled by simultaneously driving the two electro-thermal conversion elements, but assume maximal values when the bubbling timings are shifted by a period as very short as 0.1 to 0.3 xcexcs.
When the bubbling timings upon driving the electro-thermal conversion elements are shifted by a predetermined period by utilizing this phenomenon, the ink ejection velocity and ejection amount can be increased while energy applied to the electro-thermal conversion elements is the same as that upon simultaneously driving them. As a result, landing precision or the like can be improved.
As will be described in the following embodiments, the refill frequency can be greatly improved depending on the layout of the electro-thermal conversion elements or their bubbling order, and high-speed recording can also be realized.
Since the drive timings of the electro-thermal conversion elements, and the ink bubbling timings have a predetermined relationship therebetween, the same control as for the ink bubbling timings applies to the drive timings of the electro-thermal conversion elements.
As a drive pulse of each electro-thermal conversion element, a single pulse normally used, and a double pulse made up of a pre-heat pulse for controlling bubbling of ink by controlling the temperature distribution of ink in the vicinity of the electro-thermal conversion element, and a main heat pulse for bubbling the ink, are known. All the electro-thermal conversion elements may be driven by an identical pulse or a single pulse may be applied to at least one of two or more electro-thermal conversion elements to be driven and a double pulse may be applied to other elements, so as to enhance the size differences of dots upon gradation expression. In the latter case, when electro-thermal conversion elements are arranged at different distances from each ejection orifice, it is preferable to apply a single pulse to the electro-thermal conversion element near the ejection orifice, and to apply a double pulse to the electro-thermal conversion element far from the ejection orifice.
Furthermore, the ink-jet recording head and ink-jet recording apparatus of the present invention comprise means for relatively shifting the bubbling timings to obtain the same ink ejection velocity or ejection amount as that obtained when ink is bubbled by simultaneously driving the electro-thermal conversion elements. With this arrangement, even when the ink-jet recording head of the present invention is mounted on either an ink-jet recording apparatus which uses an ink-jet recording head having one electro-thermal conversion element in correspondence with one ink channel or even when an ink-jet recording head having one electro-thermal conversion element in correspondence with one ink channel is mounted on the ink-jet recording apparatus of the present invention, the ink ejection characteristics remain nearly the same, and the apparatus can record without posing any problems.